The present invention relates to metering devices for fluids; and more particularly it relates to a device which achieves highly precise metering of extremely small quantities of fluids such as that in the range of only a very few microliters or less, thereby providing special advantages and utility in the field of chemical assays of biological specimens in which precise control is very desirable as to the small amount of reagents, serum sample, or other fluids used in the assay.
It is well known that a major determinative factor regarding the amount of a biological specimen required to be used in an assay is imposed by the limitations in accuracy and precision of the measuring or metering means available to the laboratory worker; and for a long time a high degree of accuracy and precision has been particularly difficult to attain when there are only very small quantities of specimen available for the assay, such as spinal fluid specimens and blood specimens from pediatric or geriatric patients. Thus the more precise a metering means can be with respect to smallness of amount of quantities metered, the less the amount of the biological sample need be provided to the assayist or to the assay equipment. And since biological fluids, particularly blood for example, are usually difficult to obtain in large quantities (due to expense, pain, and other undesirable factors), a precision metering of very small quantities of assay fluids has been long a goal in the field of such chemical assays.
Also a minimization of sample volume, and thus also of reagent volumes, has been increasingly felt desirable as to such factors as reduction of space requirements of assay equipment and reduction in costs of the reagents themselves.
Thus, for reasons as those illustrated, a goal and achievement of the present invention is to provide high precision metering of extremely small (a microliter or less) quantities of fluids.
Further, the concepts of the present invention achieve a long-lasting durability and reliability of the equipment, thus achieving and providing long-term dependability, which is particularly advantageous in the field of bio-chemical assays whose accuracy and reliability is needed for human health and welfare, considering the diagnostic and therapeutic medical values and uses of such assays.
(In using the terms herein such as "precise", "accurate", etc., they are used in the sense of repeatability from one test to the next, in contrast to numerical exactness; although, even as to numerical exactness, that also may be generally achieved by adjustment and calibrations as herein mentioned.)